1. Field of the Invention
The present invention relates to an in-plane switching (IPS) mode liquid crystal display (LCD) device and more particularly to a color filter substrate having reduced production cost and an improved brightness property and a method of fabricating the array substrate.
2. Discussion of the Related Art
As the society has entered in earnest upon an information age, flat panel display devices, which have excellent capabilities of a thin profile, light weight and low power consumption, and so on, are introduced. Among these devices, LCD devices are widely used for notebook computers, monitors, TV, and so on, because of their high contrast ratio and characteristics adequate to display moving images.
Generally, the LCD device includes first and second substrates, which face each other, and a liquid crystal layer, which includes liquid crystal molecules, interposed therebetween. First and second electrodes are respectively formed on the first and second substrates. When voltages are applied to the first and second electrodes to generate an electric field, the liquid crystal layer is driven by the electric field such that images can be displayed by controlling light transmissivity.
FIG. 1 is an exploded perspective view of the related art LCD device. The LCD device 1 includes first and second substrates 12 and 22, and a liquid crystal layer 30. The first and second substrates 12 and 22 face each other, and the liquid crystal layer 30 is interposed therebetween.
The first substrate 12 includes a gate line 14, a data line 16, a TFT “Tr”, and a pixel electrode 18. The first substrate 12 including these elements is referred to as an array substrate 10. The gate line 14 and the data line 16 cross each other such that a region is formed between the gate and data lines 14 and 16 and is defined as a pixel region “P”. The TFT “Tr” is formed at a crossing portion of the gate and data lines 14 and 16, and the pixel electrode 18 is formed in the pixel region “P” and connected to the TFT “Tr”.
The second substrate 22 includes a black matrix 25, a color filter layer 26, and a common electrode 28. The second substrate 22 including these elements is referred to as a color filter substrate 20. The black matrix 25 has a lattice shape to cover a non-display region of the first substrate 12, such as the gate line 14 and the data line 16 on the first substrate 12. A light leakage in the non-display region is blocked by the black matrix 25. The color filter layer 26 includes first, second, and third sub-color filters 26a, 26b, and 26c. Each of the sub-color filters 26a, 26b, and 26c has one of red, green, and blue colors R, G, and B and corresponds to the each pixel region “P”. The common electrode 28 is formed on the black matrix 25 and the color filter layers 26 and over an entire surface of the second substrate 22.
As mentioned above, the LCD device 1 includes the color filter substrate 20, where the common electrode 28 is formed, the array substrate 10, where the pixel electrode 18 is formed, and the liquid crystal layer 30 interposed therebetween. The liquid crystal layer 30 is driven by a vertical electric field induced between the common electrode 28 and the pixel electrode 18. The LCD device 1 has advantages of transmissivity and aperture ratio. However, since the liquid crystal layer is driven by the vertical electric field, there is a disadvantage of a viewing angle.
An in-plane switching (IPS) mode LCD device may be used to resolve the above-mentioned limitations. FIG. 2 is a cross-sectional view of the related art IPS mode LCD device. As shown in FIG. 2, the IPS mode LCD device 40 includes first and second substrates 50 and 60, and a liquid crystal layer 70 interposed therebetween. Both a common electrode 55 and a pixel electrode 58 are formed on the first substrate 50 such that the liquid crystal layer 70 is driven by a horizontal electric field L induced between the common and pixel electrodes 55 and 58.
When the voltage is applied to the IPS mode LCD device 40, liquid crystal molecules above the common electrode 55 and the pixel electrode 58 are unchanged. But, liquid crystal molecules between the common electrode 55 and the pixel electrode 58 are horizontally arranged due to the horizontal electric field L. Since the liquid crystal molecules are arranged by the horizontal electric field L, the IPS mode LCD device 40 has a characteristic of a wide viewing angle.
A seal pattern (not shown) is formed along edges of the first and second substrates 50 and 60 after forming the above elements are formed on the first and second substrates 50 and 60. Then, the liquid crystal is injected to a space between the first and second substrates 50 and 60, and the first and second substrates 50 and 60 are attached to each other such that the IPS mode LCD device 40 is fabricated. When forming the elements on the first and second substrates 50 and 60, the first and second substrates 50 and 60 is disposed on a stage of a processing apparatus. In this case, static electricity is generated on the first and second substrates 50 and 60. Since there are electric lines and electrodes, which are formed of a metallic material, on the first substrate 50, the static electricity can be easily removed. However, since there is no element of a conductive material on the second substrate 60 for the IPS mode LCD device, there are damages on the second substrate 60 due to the static electricity. These problems are also generated in the end products. Since there is no element of a conductive material on the second substrate 60, which is referred to as a color filter substrate, the electric charge resulted from the static electricity can not be easily removed.
To resolve these problems, after a rear side electrode (not shown) is formed on a rear surface of the second substrate 60 by depositing a transparent conductive material, such as indium-tin-oxide (ITO) and indium-zinc-oxide (IZO), processes are performed on the second substrate 60. However, since ITO or IZO is very expensive, production costs are increased.
In addition, there is another problem during a rework process for the color filter substrate. When a problem is generated in the color filter layer, the black matrix or the overcoat layer, the rework process is required. ITO and IZO are not affected by an etchant for removing the color filter layer or the black matrix, while ITO and IZO are affected by an etchant from removing the overcoat layer. When a problem is generated in the color filter layer, a process for the color filter substrate is performed after removing the color filter layer and the black matrix. However, when a problem is generated in the overcoat layer, the rear side electrode of ITO or IZO is also partially removed during a removing process for the overcoat layer. Accordingly, a process for completely removing the rear side electrode is required such that production costs are also increased.